A conventionally known ordinary air clutch has a structure as illustrated in FIG. 4.
In FIG. 4 an automotive air clutch is applied to a flywheel 10. A clutch cover 12 is secured to flywheel 10, and a pressing force generated by an annular pneumatic actuator 14 in clutch cover 12 is transmitted to pressure plate 16 so as to press and hold in clutch disc 18 in between the pressure plate 16 and the flywheel 10.
The clutch disc spline fits onto an input shaft 20 of a transmission (not shown) disposed at a rear stage of the air clutch. A cylindrical shaft 24 fits onto an outer periphery of the input shaft 20 through a bushing 22. The clutch cover 12 fits onto a right end in the figure of the cylindrical shaft 24.
A right end of the cylindrical shaft 24, as viewed in FIG. 4, is surrounded by a cover 26. Chamber 28 is formed inside of the cover 26. Two air seals 30a & 30b are installed between the cover 26 and the cylindrical shaft 24, to prevent air leakage described later in details.
A control valve 32, operated by a clutch pedal 31, is interconnected to the cover 26 so that compressed air, flowing from a compressor 34 through a pressure regulator valve 36 by means of control of the control valve 32 (inching valve), is passed through a chamber 38 provided between the air seals 30a and 30b and through an inlet port 40 of the cylindrical shaft 24 to a passage 42. An outlet port 44 is interconnected to a left end of the passage 42, and the outlet port 44 is interconnected through a passage 46 formed in a thick wall of the clutch cover 12 to an air chamber 48 of the pneumatic actuator 14.
Such conventional embodiment includes problems in that its construction is complicated and the clutch disc 18 is difficult to disengage from the pressure surface of the flywheel 10 and a sharp disengagement of clutch can not be obtained.
An object of the invention is to solve the above problems and to provide a fluid clutch for carrying out clutch engagement/disengagement operation with a pneumatic actuator at the clutch disc.